1. Field of the Invention
The present invention relates to a structure of a resin-sealed (resin-encapsulated) power semiconductor device.
2. Description of the Background Art
FIG. 10 is a vertical sectional view of a first prior art resin-sealed power semiconductor device shown as mounted to a final product. In FIG. 10, the reference character 1P designates power semiconductor elements; 2AP and 2BP designate lead parts of a frame serving as electrodes; 3P designates brazing materials for bonding the power semiconductor elements 1P to an upper surface of a die pad 19P of the frame; 4P designates thin metal wires such as aluminum wires for connection between each of the electrodes 2AP and 2BP and each of the power semiconductor elements 1P or between the power semiconductor elements 1P; and 5P designates a sealing resin.
For efficient diffusion of heat from the power semiconductor elements 1P to their immediately underlying components, the thicknesses of the lead parts 2AP and 2BP of the frame and the die pad 19P are made equal and yet possibly maximized.
Further, outer leads of the lead parts 2AP and 2BP serving as electrodes are formed into a shape mountable outside the sealing resin 5P, and subjected to surface treatment such as solder plating at their predetermined portions.
After shipment, the resin-sealed power semiconductor device having the above-mentioned structure is incorporated into customer's device on the customer's premises by bonding a substrate 6P including a control circuit for controlling the semiconductor device to the plated portions of the lead parts 2AP and 2BP of the semiconductor device with solder 7P, as shown in FIG. 10. The control circuit comprises a semiconductor element (IC) 9P such as a microcomputer for controlling the power semiconductor elements 1P, and electronic components 12P such as a resistor and a capacitor.
FIG. 11 is a vertical sectional view of a second prior art resin-sealed power semiconductor device. The device of FIG. 11 differs from the device of FIG. 10 in that the device of FIG. 11 itself contains the semiconductor element (IC) 9P such as a microcomputer shown in FIG. 10, the element 9P being mounted on an inner lead of the lead frame 2BP. For customer's use of the power semiconductor device, it is also necessary to bond the control substrate 6P with all of the electronic components 12P for the control circuit mounted thereon to an outer lead tip of the power semiconductor device of FIG. 11 by soldering, as shown in FIG. 10, on the customer's premises.
(1) The first and second prior art power semiconductor devices described above present a problem such that a long path from the power semiconductor elements 1P to the electronic components 12P provided on the control substrate 6P for controlling the power semiconductor elements 1P decreases noise immunity.
(2) In the first and second prior art practices, the thicknesses of the lead parts and the die pad are made equal and yet as great as possible, as above described, for the purpose of efficiently diffusing heat generated by the power semiconductor elements 1P. To solve the above-mentioned problem (1), it is desirable that all of the multiplicity of electronic components 12P constituting the control circuit of the power semiconductor elements 1P, together with the semiconductor element (IC) 9P in the control circuit, are mounted on the inner leads of the lead parts. However, such an attempt to contain all of the components of the control circuit in the sealing resin inevitably results in a hyperfine inner lead pattern, thereby to significantly decrease a pitch between adjacent inner leads. As a result, another problem is encountered such that it is quite difficult to form such a hyperfine pattern of the inner leads which are made as thick as possible by press working, etching or the like. With increasing functionality of the power semiconductor device, the number of electronic components constituting the control circuit contributing to the increase in functionality is on the increase, and the scale of the control circuit is accordingly increasing. This requires a much finer inner lead pattern, to make the problem more serious.